Force, Motion, and Newton's Laws Quiz

Grade 7 · Science · Quiz

10-question quiz on Newton's three laws, inertia, force, and motion.

Questions

1. What is the SI unit for force?

   1. Kilogram
   2. Newton
   3. Meter per second
   4. Joule
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   Answer: Newton

   The Newton (N) is the SI unit for force. 1 N = 1 kg·m/s². It is named after Isaac Newton.

2. Newton's Third Law applies to forces on the same object.

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   Answer: False

   Newton's Third Law describes forces between TWO DIFFERENT objects — when object A exerts a force on object B, object B exerts an equal and opposite force on object A.

3. According to Newton's Second Law, force equals mass times ___.

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   Answer: acceleration

   F = ma means Force (N) = mass (kg) × acceleration (m/s²). Rearranging: a = F/m or m = F/a.

4. A 10 kg object is accelerated at 3 m/s². What is the net force applied?

   1. 3.3 N
   2. 13 N
   3. 30 N
   4. 300 N
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   Answer: 30 N

   F = ma = 10 kg × 3 m/s² = 30 N. The units work out: kg × m/s² = N.

5. Friction is an example of an unbalanced force that can stop a moving object.

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   Answer: True

   Friction is a force that acts opposite to motion. On a moving object, friction is the unbalanced force that decelerates and eventually stops it.

6. Which best explains why a passenger leans forward when a car brakes suddenly?

   1. Newton's Third Law
   2. Newton's First Law (inertia)
   3. Newton's Second Law
   4. Gravity
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   Answer: Newton's First Law (inertia)

   By Newton's First Law, your body (in motion with the car) wants to keep moving forward even when the car stops. This is inertia in action — exactly why seatbelts save lives.

7. The overall force on an object after all forces are combined is called the ___ force.

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   Answer: net

   Net force is the vector sum of all forces acting on an object. If two equal forces push in opposite directions, the net force is zero and the object doesn't accelerate.

8. An object with more mass has more inertia.

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   Answer: True

   Inertia is directly proportional to mass. A large truck is much harder to get moving (or stop) than a bicycle because it has far greater inertia.

9. If you push a wall with 50 N of force, how much force does the wall push back on you?

   1. 0 N
   2. 25 N
   3. 50 N
   4. 100 N
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   Answer: 50 N

   Newton's Third Law: if you push the wall with 50 N, the wall pushes back on you with exactly 50 N in the opposite direction. Action-reaction pairs are always equal.

10. Which of Newton's laws is sometimes called the 'Law of Inertia'?

    1. First Law
    2. Second Law
    3. Third Law
    4. Fourth Law
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    Answer: First Law

    Newton's First Law is called the Law of Inertia because it describes inertia — the natural tendency of objects to keep doing what they're doing unless a force intervenes.

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